1. Field of the Invention
This invention belongs to the field of pharmaceutical chemistry, and provides an advantageous process for preparing a group of 6-hydroxy-2-(4-hydroxyphenyl)-3-[4-(2-aminoethoxy)benzoyl]benzo[b]thiophen es. The process makes use of certain particularly advantageous protecting groups for the hydroxy groups, and provides the desired compounds in excellent yield.
2. State of the Art
Most of the compounds which are prepared by the process of this invention were taught in U.S. Pat. No. 4,133,814, of Jones and Suarez, which patent shows a number of processes for preparing them. The patent shows the use of phenacyl, halophenacyl, and alkyl protecting groups. The process of this invention has been found to be much more advantageous than those shown by the patent.
Many types of protecting groups have been proposed and used for hydroxy groups. The standard textbook, Protective Groups in Organic Chemistry, Plenum Press, New York, 1973, J. F. W. McOmie, Ed., devotes chapters 3 and 4 to the subject. Many types of protecting groups are proposed, including alkyl groups, benzoyl groups, triarylmethyl groups, trimethylsilyl groups, acetals, ketals, esters of many types, substituted esters such as haloacetates and phenoxyacetates, carbonates, sulfonates, benzylidineacetals, benzoates and substituted benzoates.